This invention relates to methods for making alloys, and particularly to a method for alloying a metal having a relatively low boiling point with more refractory metals.
There is a constant need to improve materials. In the aerospace industry considerable emphasis is placed on the strength-to-weight ratio of materials. Generally, past efforts to improve this ratio have been directed to improving strength, with little attention given to lowering the density of alloys.
More recently, research has been directed toward lowering the density of alloys. Balmuth, U.S. Pat. No. 4,248,630 discloses the alloying of lithium with aluminum by establishing a bath of molten Al, adding all alloying elements to the bath except the Li, treating the alloy melt to remove hydrogen and adding the Li to the alloy melt. The resulting alloy is said to possess lower density along with a higher modulus of stiffness.
Additions, including Li, Mg, Ca, Ba and Zn can be made readily to Al and other metals having melting points less than the boiling points of the addition metals. Difficulties increase, however, when trying to alloy such low melting point elements with more refractory metals and alloys. Generally, the low melting point elements tend to boil away as the temperature is raised to melt the more refractory materials. For example, the melting point of Ti is about 1680.degree. C. while the boiling point of Li is about 1335.degree. C. It would appear that merely combining Li and Ti in a crucible, then heating the crucible, would boil off the Li before the Ti beings to melt. Attempts have been made to avoid this problem using complex, expensive, pressurized melting equipment. What is desired is a simpler, less expensive process for reducing the density of the more refractory metals.
Accordingly, it is an object of the present invention to provide a process for producing alloys of metals having relatively low boiling points with the more refractory metals.
Other objects, aspects and advantages of the present invention will be apparent to those skilled in the art.